1. Field of the Invention
The present invention relates to a hydraulic damper, in particular to a hydraulic damper for the suspension system of a motor vehicle.
2. Background Art
Hydraulic suspension dampers typically include a tube filled with working liquid, inside of which a slidable piston assembly is placed. The piston assembly is attached to a piston rod led outside the tube through the piston rod guide, and includes a piston with rebound valve arrangement having a number of flow passages disposed around the piston at radially inner side thereof and compression valve arrangement having a number of flow passages disposed around the piston at radially outer side thereof. The valve arrangements control the flow of working liquid passing through the piston assembly during the rebound and the compression stroke of the damper.
Each valve arrangement usually includes a stack of resilient disks covering the flow passages of the piston and acting as one-way valve deflecting or moving under, the pressure of the working liquid to allow flow of fluid. Disks of the compression valve arrangement are typically of larger diameter than disks of the rebound stroke arrangement. Number shape, diameter and thickness of each disk provide an adjustable compression and rebound damping forces.
To achieve a blow-off characteristic of the damper during the rebound stroke (i.e., high digressivity of the damping force for high piston velocities), the arrangements disclosed by GB 2,314,602 and GB 2,376,514 have the deflectable disks of the rebound stroke valve are biased to a closed position by a coil spring which engages a nut which is screw threaded to the piston rod and a spring seat which is axially slidable relative to the nut and which engages the deflectable disks.